{
  "id": "UBL-SR-04",
  "country": "EU",
  "syntax": "ubl",
  "group": "syntax",
  "severity": "fatal",
  "severity_note": "fatal, from the Flag column of the Peppol BIS Billing 3.0 UBL rules index retrieved 2026-10-18.",
  "spec": "Peppol BIS Billing 3.0, May 2026 release, EN 16931 model bound to UBL",
  "statement": "Invoice object identifier shall occur maximum once",
  "statement_lang": "en",
  "context": "/ubl:Invoice | /cn:CreditNote",
  "test": "(count(cac:AdditionalDocumentReference[cbc:DocumentTypeCode='130']/cbc:ID) <= 1)",
  "meaning": "The invoice object identifier shall occur at most once. The statement has no period and says shall. The flag is fatal. The context is the same string as BR-CO-18. The published test counts additional document reference identifiers whose document type code is 130, in straight quotes. The comparison has a space before <= and a space after it.",
  "fix": "Send at most one additional document reference with document type code 130.",
  "example_fail": "The invoice has two additional document references with document type code 130.",
  "example_pass": "The invoice has one additional document reference with document type code 130, or none.",
  "example_note": "Illustration of the condition in the official statement. Not an example published by the source.",
  "source_url": "https://docs.peppol.eu/poacc/billing/3.0/rules/ubl-tc434/UBL-SR-04/",
  "source_retrieved": "2026-10-18",
  "last_verified": "2026-10-18"
}